1. Field of the Invention
This invention relates, in general, to conveyors adapted to convey articles or work pieces and, more particularly, to conveyors of the mechanical accumulating type.
2. Description of the Prior Art
Conveyors and, in particular, conveyors of the accumulating type are well known and have been employed in many manufacturing operations. In such conveyor systems for supplying articles to assembly stations it has been a practice to provide a multiplicity of stations together with means for advancing articles from station to station. Initially, means were provided that were responsive to the presence or absence of an article at each station such that when an empty station was sensed, an article was advanced from the next rearmost station to fill this empty station. This resulted in vacating the previous station with a sequence of operations being required to move rearmost articles forward and the empty station itself was moved back to the beginning of the line and eventually was eliminated by loading the conveyor at that point with a new article. For various reasons, articles are removed from intermediate stations between the loading and delivery stations along the conveyor and it is necessary that the conveyor function automatically to advance articles from the load end in order to maintain each station in a filled condition at all times. It is particularly desirable to accomplish the foregoing results by a complete mechanical sensing control and actuating means which is not subject to the unavoidable failures encountered with electrical or electronically controlled systems.
A typical conveyor system which performs the aforementioned operation may take the form of a pair of elevated and spaced parallel support frames having equally spaced support stations on which the articles are disposed. A suitable conveyor, such as a reciprocating or walking beam type, is adapted to start from an initial position at the beginning of its stroke and engage the articles, move the articles forward to the next position wherein the conveyor system disengages the articles and, finally, returns to its initial position. Generally, such systems may comprise a sensing means positioned at each station and, if the station is empty, the sensing means will position itself into an operating mode and cooperate with a suitable mechanism which will engage the articles to achieve the necessary advancement.
In such a conventional conveyor, the sensing means, typically a lever arm, is affixed to the stationary support frame at each article support station. During the forward and reverse strokes of the conveyor, the parts are slid along a frame between each support station.
It is also known to provide a lift and carry type of conveyor to lift articles over interfering plant equipment or to prevent sliding contact between the articles and the conveyor support rails. In this type of conveyor, a suitable mechanism is incorporated into the conveyor drive which initially raises the entire conveyor a predetermined distance to lift the articles off of the support rails before the forward stroke is initiated. At the end of the forward stroke, the conveyor is lowered to deposit the articles in the next advanced position along the support rails. However, since the entire conveyor is raised and lowered as a unit, no accumulation of the articles in the forwardmost positions on the conveyor can be achieved.
Thus, it would be desirable to provide an accumulating conveyor which provides lift and carry features. It would also be desirable to provide an accumulating conveyor which is designed to prevent the occurrence of a false article presence indication in a support station. Finally, it would be desirable to provide an accumulating conveyor which incorporates a simplified mechanism for transferring the articles between successive support stations.